US 3565462 A
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Feb. 23, 1971 s. H. GOTTLIEB GRAPHIC OVERLAY ASSEMBLY Filed Ju1y"l5. 1969 3 Sheets-Sheet 1 I m 3 A W v WA 0 w INVENTOR. GERALD H. GOTTLJEB "Feb. Z3, 1971 s. H. GOTTLIEB 3,555,462
GRAPHIC OVERLAY ASSEMBLY Filed July 15, 1969 3 Sheets-Sheet z NVENTOR. GERALD' H. GOTTUEB 'I'TORNEY Feb. 23, 1971 G. H. GOTTLIEB GRAPHIC OVERLAY ASSEMBLY 3 Sheets-Sheet 3 Filed July 15, 1969 &
I INVENTOR United States Patent Int. Cl. B42d N00 US. Cl. 281-3 25 Claims ABSTRACT OF THE DISCLOSURE Graphic overlay assembly for facilitating comparison of information and featuring one or more unitary sheets of film-like, tough, flexible transparent material, such as polyethylene terephthalate, each divided by a transverse hinge line into a smaller half and a larger half. The free edge of the larger half facilitates binding with other sheet material, the smaller half being imprinted with intelligence and the larger half being opaqued with or without intelligence for comparison with the intelligence on the smaller half when the latter is folded to its stored position. The binder for the overlay assemblies preferably includes a fold-out cover imprinted with a grid or other suitable reference guide positioned to underlie and register with the intelligence on the unfolded smaller half of one or more unfolded transparencies. A feature of the invention is the use of film-like transparent material suitably processed for reinforcing the film adjacent the hinge line by one of several techniques.
This invention is a continuation-in-part of my copending application for United States Letters Patent, Ser. No. 496,922. filed Oct. 18, 1965 entitled Graphic Display Device and subsequently abandoned.
This invention relates to graphic display devices and more particularly to an improved unitary folding binder device for supporting a plurality of folding transparencies each containing intelligence and so arranged that the intelligence on any two or more transparencies selected at random can be easily and quickly brought into true registration for convenience While comparing and studying the information thereon.
There are a great variety of situations where it is desirable to evaluate information present on any two or more sheets. These needs are so numerous and so Widely different that it is not practical to do more than mention typical examples. For example, economists have frequent need for comparing charts and graphs, the same is true for teachers who wish to evaluate assorted information in any particular field; engineers often wish to compare data and performance characteristics of similar components under differing conditions; the same is true of manufacturers who have need for studying and evaluating production rates, inventory requirements and other data. Other fields include text books, reference books, encyclopedias and books generally.
The present invention, in one preferred embodiment, utilizes three cover plaques hinged together along the opposite lateral edges of a central member. One of these hinge areas includes looseleaf binder means of any suitable character in which are mounted any desired number of unitary sheets of flexible transparent material. In other applications of the invention, the transparent assemblies may be bound together with other sheet material in con ventional manner well known to the book binding art. Each sheet is formed in two parts, the outer part being hinged to the inner part parallelto the binder device and being embossed, printed or otherwise provided With suitable intelligence. The size of the folded sheets corresponds generally with the surface area of the cen- 3,565,462 Patented Feb. 23, 1971 tral cover section in order that sheets not needed for a particular comparison can be folded over against the central section while those selected for use are unfolded and superimposed upon one another for comparative analysis. Appropriate means are preferably provided for holding each of the unfolded transparencies in predetermined registry With one another and with reference guide means such as a grid fixed to the inside of the cover leaf. In this manner any number of transparencies can be compared while those in use remain folded and lying against the center portion of the device cover.
Additional features of the present invention include several highly effective modes of making the individual sheets from one-piece transparent flexible material each provided with a hinge dividing the page into two halves of different size. Desirably the larger half of each transparency is suitably opaqued and imprinted with a grid or other standard background reference material useful in the expeditious interpretation of the graphical information on the transparent outer half of the sheet when the information contained on only a single transparency is of interest. Also, the binder means holding the sheet detachably assembled is highly advantageous and permits different sets of either related information to be substituted and compared readily.
It is found that exceedingly tough and durable transparent films having a thickness of as small as one and two mils are highly satisfactory, particularly when processed in accordance with the principles of this invention to stiffen them along the hinging area in a manner assuring repeated hinging along the same hinge axis. This stiffening can be accomplished in several different ways in cluding laminating the transparency to another sheet slit coincident with the desired hinge axis and providing a pair of edges in abutment when the transparency is unfoldedfrom a position wherein its unslit halves lie against one another. The stiffening layer may comprise either a transparent or a non-transparent sheet. In the former case, the larger half of the laminated assembly may be opaqued with a pigmented layer or by other means. If a transparent sheet is employed to stiffen the hinge areas, it is preferably coextensive in size with the main transparency but need not be laminated to the transparent intelligence-bearing area of the smaller outer half of the overlay assembly. stiffening of the transparency may also be accomplished using a coating applied along at least strip areas of the transparency closely spaced to either side of the hinge axis, as well as by a combination of any two of the men tioned stiffening techniques.
Accordingly it is a primary object of the present lnvention to provide an improved device for facilitatingcomparison of information on any of a plurality of similar sheets each provided with different intelligence.
Another object of the invention is the provision of a graphical display device designed for compact foldmg when not in use and containing a plurality of sheets of transparent material each provided with intelligence thereon and so arranged that any of a plurality of sheets selected at random can be brought quickly into superlmposed registry while comparing information on these sheets.
Another object of the invention is the provision of a graphical display device having a cover formed in three principal parts hingedly interconnected and including ring or other binder means along one hinge adapted to hold a plurality of foldable sheets of transparent material each provided with intelligence thereon and including means for bringing selected sheets of information into surface contact while the information thereon is being evaluated.
Another object of the invention is the provision of a plurality of graphical display assemblies each comprising a one-piece sheet of transparent material hinged to divide the same into halves of unequal areas each carrying intelligence and including a reference guide for use in interpreting this intelligence when the sheets are in their normal folded conditions, the similar assemblies being bound together along one edge and so arranged that more than one sheet can be unfolded and superimposed for comparative study.
Another object of the invention is the provision of a folding overlay assembly having a main body formed by a single sheet of transparent film-like resinous material folded transversely thereof along a hinge line offset to one side of the transverse center and stiffened at least along one edge of the hinge line to resist hinging except along the hinge axis and to counteract the memory properties of the hinge area.
Another object of the invention is the provision of a folding overlay comprising a single body sheet of transparent film folded along a hinge line offset from its transverse center to form halves of unequal size and stiffened by an adherent layer covering said larger half and a portion of said smaller half except for a narrow gap coinciding with the axis of the hinge line, and said stiffening layer preferably being opaque.
Another object of the invention is the provision of a folding overlay assembly comprising a pair of transparent film-like sheets laminated to one another and including a transverse integral hinge dividing said assembly into a large and a smaller half and formed by a portion of one of said sheets coinciding with a slit extending through the other of said sheets with the slit edges abutting one another when said halves are unfolded to lie in a common plane and discouraging backfolding.
These and other more specific objects will appear upon reading the following specification and claims and upon considering in connection therewith the attached drawings to which they relate.
Referring now to the drawings in which a preferred embodiment of the invention is illustrated.
FIG. 1 is a generally perspective view of the graphical display device according to a preferred embodiment showing the device opened and ready for use;
FIG. 2 is an end elevational view of the device in open position and showing some of the sheets in lifted position;
FIG. 3 is a plan view of one of the information sheets in open position as viewed from the top surface thereof;
FIGS. 4, and 6 are top plan views of the device in open position and with different ones of the sheets thereof in open position, FIG. 4 showing the covers only in open position, FIG. 5 showing a single one of the transparencies in reading position, and FIG. 6 showing two of the transparencies held rigidly in registration and reading position;
FIG. 7 is a top plan view of a second preferred embodiment of the invention folding overlay assembly in open position;
FIG. 8 is an edge elevational view of the FIG. 7 assembly on an enlarged scale and prior to lamination of the components; and
FIG. 9 is an exploded view in perspective of the components and showing both halves of the one-piece transparency imprinted with intelligence.
Referring initially and more particularly to FIG. 1, there is shown on illustrative embodiment of the invention device designated generally 10. This device includes a stiff unitary cover having a central section 11 and two covers 12, 13 hinged to its opposite lateral edges along the double hinged sections 14, 15. Hinge section 15 is provided with any suitable binder means for sheet material, as for example, a ring binder 17 having any known means for opening the rings thereof for the reception and substitution of sheets of intelligence.
It will be understood that binder means 17 may be associated with either of the double hinges 14 and 15, it being immaterial or a matter of personal choice whether the binding is on one or the other side of the center plaque. Associated with the cover remote from the binder are suitable registration means, such as the posts or bosses 19, 19. These project upwardly from the interior surfaces of the binder and are accurately positioned to extend into openings or notches formed in each of the transparencies when unfolded and coperating therewith in a manner to be described more fully below to hold these sheets in accurate registry with one another and With guide reference means while being interpreted.
Desirably the inner surface of cover 12 is Provided with suitable means for use in interpreting the information on the transparencies. Typically and representative of such assisting devices is the grid work 20 comprising equally spaced sets of vertical and horizontal lines. However, it will be understood that the grid work is merely representative of many graphical interpretation aid devices. For example if the device were being used to show the internal construction of an engine with different parts in position relative to the main housing, then the grid work might well comprise a vertical cross-section showing the engine housing with all or some parts removed. In this case the different transparencies would show different ones of them missing components of this engine and these could then be assembled into the engine body by superimposition of a selected showing upon the crosssection view of the engine housing.
A typical unitary transparency sheet 25 is best shown in FIG. 3. One lateral margin, as the left-hand margin is sufficiently wide for a binding or mounting purpose and is here illustrated as provided with a row of holes 26 fitting loosely over rings 17 of the binder. If the overlay assembly is to be bound with other sheets, perforations 26 may be omitted and the mounting edge stitched, bonded or otherwise secured to the other overlays. The sheet includes an inner or larger half 27 and an outer or smaller half 28 connected by a hinge line 29 offset slightly to one side of the transverse center and parallel to the lateral edges. Sheet 25 is formed in one piece of any suitable flexible transparent material of which there are various suitable types readily available on the open market, particularly among the transparent plastic compositions. Desirably the material should be smooth and have a sufficiently high durometer to form a hinge 29 having a long service life. A particular tough and durable material meeting the rigorous requirements of text book and encyclopedia applications is provided by polyethylene terephthalate resin available commercially under the trade name of Mylar from E. I. du Pont de Nemours Co. This material may be used in thicknesses of less than 1 to several mils. It is readily folded to form a permanent hinge line capable of being folded and unfolded repatedly without fatigue or failure. This material is readily laminated or coated with a stiffening layer to discourage the formation of additional hinge lines and to facilitate rapid and precise hinging along the original hinge axis and to counteract memory characteristics of the transparent plastic material.
According to one technique, sheets 25 are coated on their upper face with an opaque or pigmented layer 30 covering substantially all of larger half 27 and preferably the marginal edges of smaller half 28. Any suitable coating material may be employed of a type printable with a contrasting color and having a thickness effective to stiffen the transparency 25 to provide desirable differential stiffness between the uncoated hinge line and the coated or layered material to either side thereof. In other Words a narrow strip or line 31 bridging hinge 29 is preferably left uncoated to facilitate the hinging action. Coating 30 on half 27 is usually accurately imprinted with the same reference guide as is applied to the surface cover member 12. Thus by way of illustration, half 27 is here shown as provided with a grid 20' identical with grid 20 on cover 12. This is so positioned as to directly underlie the transparent area 33 of half 28 when the sheet is in its normal folded position illustrated in FIG.
4. One surface of the transparent area 33 and preferably the rear face thereof is imprinted with any suitable information as for example a growth line 34. This information is imprinted in such manner as to read generally from left to right when folded either against the reference material 20' imprinted on the first half of each sheet or against reference guide 20 imprinted on the interior of cover 12. For this reason when the transparency is unfolded in the position shown in FIG. 3, the information is reversed because this it not the intended position of use.
To assure proper registration of the information with the reference guide when unfolded, each of the sheets is preferably provided with one or more openings at a suitable location for engagement over fixed posts or bosses such as bosses 19, 19. As herein shown these registration openings are shown at 36 and are generally V-shaped. Each opening preferably includes a keyhole portion 37 at its apex to avoid placing undue strain on hinge 29 during handling of the transparencies. Circular portions 37 avoid concentration of the stress directly along the hinge axis and premature failure of the hinge from this cause.
Although the registration openings are shown at the opposite ends of the hinge line, it will be understood that they may be located elsewhere, as for example, along the right-hand margin of half 28 when in its open position as shown in FIG. 3. In this case the registration post would be located along the left-hand margin of open cover 12. Of importance is the fact that the registration openings and the cooperating boss or bosses are so positioned with respect to rings 17 as to hold the sheets accurately in a predetermined position with the intelligence on transparency 33 in registration with the reference guide such as grid work 20.
To make use of the device covers are unfolded and the transparencies are overturned against cover 13 as shown in FIG. 4. Assuming that the user wishes to compare intelligence on the top sheet with that on the fifth sheet, he unfolds the top sheet and places notches 36 over bosses 19 so that growth line 34 is in accurate registry with the underlying grid 20. The next three transparencies are then turned over against the center plaque 11 of the cover unit without being unfolded and superimposed on unfolded sheet No. 1 and over the registration posts 19 in the same manner as described for that sheet. This brings the particular graphical display 38 on that sheet into registry with grid 20 and enables the user to compare the one set of information with the other in a manner made clear by FIG. 6. As will be appreciated, selected additional sheets can be unfolded against sheets 1 and 5 if the user so desires.
If the user is only interested in the information contained on a single transparency, such information can always be studied against its own reference guide without unfolding the-transparency because the reference guide is always present in accurately registered relation to the information on its associated transparency.
If the user wants to make comparison between information contained on transparencies present in the other sets thereof he need but replace the set then present in binder 17 with a selected new set of transparencies.
Referring now to FIGS. 7 and 8 there is shown a second illustrative embodiment of the invention comprising a laminated overlay assembly designated generally This assembly comprises a first or main body sheet and an identical size second sheet 41 superimposed and laminated to one another by a large area layer of suitable bonding material 42 and a second relatively narrow strip 43 of the same bonding material. The flexible sheets or films 40, 41 are of suitable transparent material, as polyethylene terephthalate, of 1 mil or greater in thickness having a width corresponding to the maximum length of the rectangular overlay assemblies 25'. Strip film material of this character can be readily assembled from supply rolls of the continuous strip material arranged to be fed into superimposed relation against the opposite surfaces of two parallel layers of pigmented bonding agent 42, 43 and held pressed together while the agent takes a set. Initially both strips of transparent material 40, 41 are in one piece but during the laminating procedure just referred to, it is desirable to slit the lower strip or sheet 41 as indicated at 45 directly opposite and coincident with the hinge line 29 in top sheet 40. In FIG. 8 slit 45 is shown as a gap but it will be understood that, preferably, the edges of the slit are in direct supporting abutment with one another when assembly 25 is opened to lie in a common plane as in indicated in FIG. 8. it will therefore be recognized that an attempt to fold the outer half 28 of the overlay in a clockwise direction about hinge 29', as viewed in FIG. 8, will be resisted by the abutting edges of slit 45 in lower sheet 41. Contrarywise, if the outer half 28 is folded upwardly counterclockwise toward half 27' then slit 45 readily opens and the overlay hinges easily and readily about hinge line 29. The transparent central area of sheet 28 is imprinted with intelligence, such as the graph line 34', and this is readily studied and interpreted in the folded condition of the overlay against the guide reference imprinted on the larger inner half 27' such as the grid 20'.
It will be appreciated from the foregoing description of FIGS. 7 and 8 that this embodiment of the invention provides an overlay assembly 25 of uniform thickness throughout its entire area and is readily fabricated from the strips of very thin, tough, transparent material laminated together in the manner described to provide added stiffness as well as opaqueness in selected areas. Both halves of the overlay can be imprinted with intelligence simultaneously thereby assuring highly precise relative positioning of the printing on both the larger inner half 27 and the smaller outer half 28'. The second sheet 41 of the overlay stiffens and re-inforces the main body film 40 and, additionally, the abutting edges of the slit 45 formed in the reinforcing sheet adds very substantially to the stiffening and flatness of the assembly when in open position, it being self-apparent that the abutting edges resist refolding the overlay in the wrong direction.
From the foregoing description of FIGS. 7 and 8 it will be recognized that substantially the full advantages of this two layer laminate can be enjoyed using a strengthening sheet of either transparent or opaque material having a size corresponding to that of the bonding agent layer 42 in FIG. 8. In other words, the stiffening strip, of paper, pigmented coating or the like, is coextensive in size with the larger half 27' of the overlay plus the width of the narrow strip of adhesive to the right of hinge line 29. In this arrangement the portion of the outer half 28- to the right of the right-hand margin of adhesive 42 is omitted. However, the strip of reinforcing material to either side of hinge line 29 provides the desired stiffening and memory countering action for hinge line 29 and safeguards against the formation of additional hinge lines close to or crossing the original hinge line 29.
It will also be appreciated from the foregoing that if the stiffening sheet just described in the preceding paragraph is opaque then either a pigmented or a non-pigmented or transparent adhesive may be used as the laminating agent. It will also be understood that the mounting or binding edge 46 of assembly 25 may be provided with binder perforations 26 for use in a ring binder or this edge may be stitched, bonded or otherwise bound to other similar assemblies or to sheets of printed material in accordance with customary bookbinding practice. In this event a group of assemblies 25' might be bound into the book in close proximity to one another in order that any selected one or more of the smaller halves of the transparencies can be folded outwardly into superimposed relation so that the intelligence thereon can be conveniently brought into registry for study and comparison.
It will also be understood that the stiffening lamination or coating layer may be confined to either side of hinge line 29' or to a strip along either side. When using an opaque strip to stiffen the hinge line, a very narrow gap coinciding with the hinge axis is preferably left uncoated or otherwise provided to avoid bridging the gap with the stiffening layer.
While the particular graphic display assembly herein shown and disclosed in detail is fully capable of attaining the objects and providing the advantages hereinbefore stated, it is to be understood that it is merely illustrative of the presently preferred embodiment of the invention.
1. A folding graphic overlay comprising a unitary onepiece sheet of flexible transparent film material having a free edge and a parallel binding edge adapted to be secured to the binding edges of a book containing other flexible sheet material, said sheet having a knife-edge-like hinge line offset slightly from the centerline thereof and parallel to said free edge thereby providing a smaller half and a larger half disposed one on either side of said hinge line, said larger half having a second layer laminated thereto generally coextensive in size with the major area of said larger half and including an edge immediately contiguous to and substantially coinciding with said hinge line and effective to stiffen said larger half adjacent said hinge line to facilitate the repeated refolding of said halves along the same hinge line between a first position wherein said smaller half lies flush against said larger half and a second position wherein said halves are unfolded to lie flat in a common plane, and said smaller half being generally transparent and imprinted with intelligence which is readable only when said halves are unfolded.
2. A folding overlay as defined in claim 1 characterized in that said one-piece sheet of flexible transparent material comprises polyethylene terephthalate film.
3. A folding overlay as defined in claim 1 characterized in that one face of said second layer is imprinted with guide reference indicia registrable with the intelligence imprinted on said smaller half.
4. A folding overlay as defined in claim 1 characterized in that said second layer comprises a sheet of opaque paper bonded to said larger half.
5. A folding overlay as defined in claim 1 character ized in that said smaller half of said transparent sheet includes a stiffening layer applied at least along the edge thereof contiguous to said hinge line and cooperating with the adjacent portion of said second layer to facilitate the repeated hinging of said transparent sheet along said hinge line.
6. A folding overlay as defined in claim 1 characterized in that said second layer comprises an opaque imprintable layer on the exterior thereof.
7. A folding overlay as defined in claim 1 characterized in that said second layer is opaque and adherent to said larger half of said transparent sheet.
8. A folding overlay as defined in claim 1 characterized in that said second layer is laminated to the larger half of said transparent sheet with a pigmented bonding agent.
9. A folding overlay comprising a unitary one-piece sheet of flexible transparent material having a free edge and a parallel binding edge adapted to be secured to the binding edges of other flexible sheet material, said sheet having a hinge line offset slightly from the centerline thereof and parallel to said free edge thereby providing a smaller half and a larger half disposed one on either side of said hinge line, said larger half having a second layer laminated thereto generally coextensive in size with the major area of said larger half and including an edge substantially coinciding with said hinge line and effective to stiffen said larger half adjacent said hinge line to facilitate the repeated refolding of said halves along the same hinge line, the smaller half of said transparent sheet includes an adherent frame-forming layer along the perimeter thereof effective to stiffen the same with one outer edge thereof terminating closely parallel to said hinge line and cooperating with the adjacent edge of said second layer of said larger half to facilitate folding said sheet accurately along said hinge line, and said smaller half being generally transparent and imprinted 'with intelligence.
10. A folding overlay comprising a unitary one-piece rectangular first sheet of film-like transparent material having a hinge line extending transversely thereof and offset slightly from the transverse centerline thereof and dividing said sheet into a larger and a smaller half with the free edge of the larger half being adapted for binding between the bound edges of other sheet material, a second sheet laminated to said larger half effective to stiffen the latter, stiffening sheet material laminated to said smaller half with one edge thereof substantially abutting the adjacent edge of said sheet along and immediately contiguous to said hinge line when said larger and smaller halves lie open in a common plane, said laminated portions serving to stiffen said transparent sheet adjacent said hinge line and facilitating folding said smaller half in a direction to bring the exposed surfaces of said transparent sheet together and to open the adjacent edges of said stiffened sheets away from one another.
11. A folding overlay as defined in claim 10 characterized in that said stiffening sheet laminated to said larger half is rendered opaque by pigmentation.
12. A folding overlay as defined in claim 10 characterized in that said stiffening sheet laminated to said larger half is bonded to said larger half by pigmented bonding agent.
13. A folding overlay as defined in claim 10 characterized in that said one-piece transparent sheet comprises a dimensionally stable film of polyethylene terephthalate.
14. A folding overlay as defined in claim 10 characterized in that said second sheet is coextensive in size with said first sheet and laminated together at least along either lateral side of said hinge line and along each transverse end of said rectangular assembly.
15. A folding overlay as defined in claim 10 characterized in that all laminated surfaces of said first and second sheets are opaque, and in that the remainder of the smaller half of said first sheet is transparent, and one of the non-laminated portions of said first and second transparent sheets being imprinted with intelligence.
16. A device for facilitating comparison of information present on two or more transparencies in close superimposition, said device comprising a binder having means for holding a series of transparencies hinged thereto, a plurality of single-piece sheet plastic transparencies held assembled within said binder each having first and second parts made of the same material folded along a transverse hinge line and having cooperating indicia on the unbound end half of each sheet precisely located relative to the associated hinge line and to indicia on other of said transparencies thereby to assure accurate registry of indicia of two or more of said transparencies when unfolded from the bound edge thereof to lie against one another in superimposed relation, said second part having information thereon and being normally folded compactly against said first part, said binder including a cover having first and second parts adapted to be unfolded aloug an axis closely adjacent the hinge between the first and second parts of said transparencies, two or more of said transparencies selected at random being unfoldable to bring their second parts into surface contact with one another against the unfolded second part of said cover, and registration means on said cover closely adjacent the opposite ends of the hinge between the parts of said transparencies positioned to register with cutouts in said transparencies when the latter are unfolded and cooperating therewith to hold the same in predetermined registry for accurate comparison of the information thereon.
17. A device as defined in claim 16 characterized in that said first part of said transparencies has an opaque coating and in that said second part has an opaque border extending along the rim portions thereof.
18. A device as defined in claim 16 characterized in that said binder includes a plurality of rings receivable loosely in a row of openings along one lateral edge of the second part of said transparencies.
19. A device as defined in claim 16 characterized in that the rear surface of the first part and the border portion of the second part of said transparencies when opened are coated with an opaque coating, the central portion of said second part being uncoated and imprinted With information readable through the transparency when said second part is unfolded and laid flat against the unfolded second part of said cover.
20. A device for comparing graphically displayed material imprinted on flexible transparent sheet material, said device comprising a unitary stiff cover assembly made in three principal parts including a central plaque and first and second cover plaques hinged to its opposite lateral edges, looseleaf binder means extending along the hinge between said central and second plaque, a plurality of sheets each comprising a single plaque of homogenous transparent plastic material held loosely but removably assembled in said looseleaf binder means, each of said sheets including inner and outer integral halves hinged together along a fold axis formed in said transparent plastic material and parallel to but remote from said binder means and the two halves being normally folded together, the inner of said halves being coated with a film of opaque material, the outer of said halves having information imprinted on one face thereof and being unfoldable to lie flat against the inner face of said first cover plaque in the open position of the latter, and registration means projecting upwardly from the inner face of said open cover adjacent the hinge axis between the tWo halves of said sheets of transparent plastic and receivable in an opening in unfolded ones of said sheets and cooperating therewith to hold a plurality of the extended halves of said sheets accurately registered in pre-determined open positions supported against the inner face of said first cover plaque so that information on each of the superimposed transparencies can be compared.
21. A device as defined in claim 20 characterized in that said registration means includes a pair of openings adjacent the upper and lower margins of each of said sheets, a pair of complementally shaped posts secured to said stiif cover and projecting upwardly from the interior surface of said cover in position to extend into said openings to hold the sheets in predetermined position when engaged over said posts.
22. A unitary one-piece sheet of flexible transparent plastic material folded over against itself along an integral hinge line offset slightly from the centerline of said sheet to provide a mounting strip along the edge of the larger half parallel to and remote from said hinge, said larger half being covered with a coating of opaque material imprinted with reference guide means on its upper face, and the smaller of said halves being imprinted with intelligence in accurate registry with said reference guide means when said smaller half is folded over on top of said larger half.
23. A unitary sheet of material as defined in claim 22 characterized in that said reference guide means is imprinted on a coating of opaque material covering said larger half of the transparent material, and a border of opaque material surrounding the rim of said smaller half.
24. A unitary sheet of material as defined in claim 22 characterized in the provision of keyhole openings in said sheet extending toward one another from the opposite ends of said hinge.
25. A folding overlay comprising a unitary one-piece flexible transparent material having a free edge and a binding along the opposite lateral edge thereof adapted to be secured to the binding edges of other flexible sheet material, said sheet having a hinge line thereacross between said binding edge and said free edge and parallel thereto, a second sheet of flexible material laminated to said sheet of transparent material and including a slit extending from edge to edge thereof and superimposed directly on said hinge line, the edges of said slit being in direct abutting relation to one another when said hinge is fully open with said laminate lying substantially in the same plane and thereby effective to resist folding said laminate except in a direction to open said slit edges away from one another.
References Cited UNITED STATES PATENTS 2,155,924 4/1939 Barrett et al. 35-53 2,262,796 11/ 1941 Cavalero 281-29 2,309,244 1/1943 Fey 281-38 2,411,368 11/1946 Dow 281-29UX 2,793,442 5/1957 Ozga 40-158X 3,069,746 12/1962 Scharf 161-6 3,091,046 5/ 1963 Engelstein 40102 3,320,225 5/ 1967 Bradbury 281-37UX FOREIGN PATENTS 16,039 1915 Great Britain 35-40 421,347 12/ 1934 Great Britain 35-26 989,598 4/ 1965 Great Britain 40360 HARLAND S. SKOGQUIST, Primary Examiner US. Cl. X.R. 35-50; 281-38